I have and the IQ of the new GH4 is said to be the same as the E-M1 and E-M5's, ie. also the same as the GX7 or the E-M10, E-PM2... give and take a tiny bit due to imrpoved processor speed and tweaking. There is very little in it, whatever Panasonic tries to tell us in any IQ improvement. They have also tried to tell us about such improvements in the G6 (compared to the IQ of the same sensor on the GH2 and G5). The fact is, there is no evidence yet of any real improvement that is worth mentioning so far in any of the M43 cameras since the E-M5 1.5 years ago. All the tweaking, better processor/processing, weaker or removal of the AA filter, etc all did just about nothing that is worth mentioning. We still need to read the reviews of the GH4 but there is almost certainly no real IQ improvement.

Then you will have to redefine "better" because according to your definition, all current APS-C sensors from the last 2 years are the same...--Duarte Bruno